Python dictionary are keys and values always the same order

Question

It looks like the lists returned by keys   and values   methods of a dictionary are always a 1-to-1 mapping  assuming the dictionary is not altered between calling the 2 methods    For example    gt  gt  gt  d     one  1   two   2   three   3   gt  gt  gt  k  v   d keys    d values    gt  gt  gt  for i in range len k        print d k i      v i   True True True   If you do not alter the dictionary between calling keys   and calling values    is it wrong to assume the above for-loop will always print True   I could not find any documentation confirming this

User · Answer

Good references to the docs  Here s how you can guarantee the order regardless of the documentation   implementation   k  v   zip  d iteritems

User · Answer

Found this      If items    keys    values      iteritems    iterkeys    and   itervalues   are called with no   intervening modifications to the   dictionary  the lists will directly   correspond    On 2 x documentation and 3 x documentation

User · Answer

Yes  what you observed is indeed a guaranteed property -- keys    values   and items   return lists in congruent order if the dict is not altered   iterkeys    amp c also iterate in the same order as the corresponding lists

User · Answer

Yes it is guaranteed in python 2 x      If keys  values and items views are iterated over with no  intervening   modifications to the dictionary  the order of  items will directly   correspond

User · Answer

Yes  Starting with CPython 3 6  dictionaries return items in the order you inserted them    Ignore the part that says this is an implementation detail  This behaviour is guaranteed in CPython 3 6 and is required for all other Python implementations starting with Python 3 7

User · Answer

For what it s worth  some heavy used production code I have written is based on this assumption and I never had a problem with it  I know that doesn t make it true though  -   If you don t want to take the risk I would use iteritems   if you can   for key  value in myDictionary iteritems        print key  value

User · Answer

According to http   docs python org dev py3k library stdtypes html dictionary-view-objects   the keys    values   and items   methods of a dict will return corresponding iterators whose orders correspond  However  I am unable to find a reference to the official documentation for python 2 x for the same thing   So as far as I can tell  the answer is yes  but only in python 3 0

User · Answer

I wasn t satisfied with these answers since I wanted to ensure the exported values had the same ordering even when using different dicts   Here you specify the key order upfront  the returned values will always have the same order even if the dict changes  or you use a different dict   keys   dict1 keys   ordered keys1    dict1 cur key  for cur key in keys  ordered keys2    dict2 cur key  for cur key in keys

[python] Python dictionary: are keys() and values() always the same order?

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